feat: add Board Planning module with investment/assessment scenario modeling

Implements Phase 11 Forecasting Tools - a "what-if" scenario planning system
for HOA boards to model financial decisions before committing.

Backend:
- 3 new tenant-scoped tables: board_scenarios, scenario_investments, scenario_assessments
- Migration script (013) for existing tenants
- Full CRUD service for scenarios, investments, and assessments
- Projection engine adapted from cash flow forecast with investment/assessment deltas
- Scenario comparison endpoint (up to 4 scenarios)
- Investment execution flow: converts planned → real investment_accounts + journal entry

Frontend:
- New "Board Planning" sidebar section with 3 pages
- Investment Scenarios: list, create, detail with investments table + timeline
- Assessment Scenarios: list, create, detail with changes table
- Scenario Comparison: multi-select overlay chart + summary metrics
- Shared components: ProjectionChart, InvestmentTimeline, ScenarioCard, forms
- AI Recommendation → Investment Plan integration (Story 1A)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

db/migrations/013-board-planning.sql

@@ -0,0 +1,83 @@
+-- Migration 013: Board Planning tables (scenarios, investments, assessments)
+-- Applies to all existing tenant schemas
+
+DO $$
+DECLARE
+  tenant_schema TEXT;
+BEGIN
+  FOR tenant_schema IN
+    SELECT schema_name FROM information_schema.schemata
+    WHERE schema_name LIKE 'tenant_%'
+  LOOP
+    -- Board Scenarios
+    EXECUTE format('
+      CREATE TABLE IF NOT EXISTS %I.board_scenarios (
+        id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+        name VARCHAR(255) NOT NULL,
+        description TEXT,
+        scenario_type VARCHAR(30) NOT NULL CHECK (scenario_type IN (''investment'', ''assessment'')),
+        status VARCHAR(20) DEFAULT ''draft'' CHECK (status IN (''draft'', ''active'', ''approved'', ''archived'')),
+        projection_months INTEGER DEFAULT 36,
+        projection_cache JSONB,
+        projection_cached_at TIMESTAMPTZ,
+        created_by UUID NOT NULL,
+        created_at TIMESTAMPTZ DEFAULT NOW(),
+        updated_at TIMESTAMPTZ DEFAULT NOW()
+      )', tenant_schema);
+
+    -- Scenario Investments
+    EXECUTE format('
+      CREATE TABLE IF NOT EXISTS %I.scenario_investments (
+        id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+        scenario_id UUID NOT NULL REFERENCES %I.board_scenarios(id) ON DELETE CASCADE,
+        source_recommendation_id UUID,
+        label VARCHAR(255) NOT NULL,
+        investment_type VARCHAR(50) CHECK (investment_type IN (''cd'', ''money_market'', ''treasury'', ''savings'', ''other'')),
+        fund_type VARCHAR(20) NOT NULL CHECK (fund_type IN (''operating'', ''reserve'')),
+        principal DECIMAL(15,2) NOT NULL,
+        interest_rate DECIMAL(6,4),
+        term_months INTEGER,
+        institution VARCHAR(255),
+        purchase_date DATE,
+        maturity_date DATE,
+        auto_renew BOOLEAN DEFAULT FALSE,
+        executed_investment_id UUID,
+        notes TEXT,
+        sort_order INTEGER DEFAULT 0,
+        created_at TIMESTAMPTZ DEFAULT NOW(),
+        updated_at TIMESTAMPTZ DEFAULT NOW()
+      )', tenant_schema, tenant_schema);
+
+    -- Scenario Assessments
+    EXECUTE format('
+      CREATE TABLE IF NOT EXISTS %I.scenario_assessments (
+        id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+        scenario_id UUID NOT NULL REFERENCES %I.board_scenarios(id) ON DELETE CASCADE,
+        change_type VARCHAR(30) NOT NULL CHECK (change_type IN (''dues_increase'', ''special_assessment'', ''dues_decrease'')),
+        label VARCHAR(255) NOT NULL,
+        target_fund VARCHAR(20) CHECK (target_fund IN (''operating'', ''reserve'', ''both'')),
+        percentage_change DECIMAL(6,3),
+        flat_amount_change DECIMAL(10,2),
+        special_total DECIMAL(15,2),
+        special_per_unit DECIMAL(10,2),
+        special_installments INTEGER DEFAULT 1,
+        effective_date DATE NOT NULL,
+        end_date DATE,
+        applies_to_group_id UUID,
+        notes TEXT,
+        sort_order INTEGER DEFAULT 0,
+        created_at TIMESTAMPTZ DEFAULT NOW(),
+        updated_at TIMESTAMPTZ DEFAULT NOW()
+      )', tenant_schema, tenant_schema);
+
+    -- Indexes
+    EXECUTE format('CREATE INDEX IF NOT EXISTS idx_%s_bs_type_status ON %I.board_scenarios(scenario_type, status)',
+      replace(tenant_schema, '.', '_'), tenant_schema);
+    EXECUTE format('CREATE INDEX IF NOT EXISTS idx_%s_si_scenario ON %I.scenario_investments(scenario_id)',
+      replace(tenant_schema, '.', '_'), tenant_schema);
+    EXECUTE format('CREATE INDEX IF NOT EXISTS idx_%s_sa_scenario ON %I.scenario_assessments(scenario_id)',
+      replace(tenant_schema, '.', '_'), tenant_schema);
+
+    RAISE NOTICE 'Board planning tables created for schema: %', tenant_schema;
+  END LOOP;
+END $$;